Robert Wilton <[email protected]> writes: > On 14/02/2017 14:08, Christian Hopps wrote: >> Robert Wilton <[email protected]> writes: >> >>> Hi tags draft authors, >>> On 09/02/2017 12:28, Lou Berger wrote: >>>> I'm personally more excited by the use of tags as additional module >>>> meta-data accessible via yang library. But also see no reason to >>>> preclude this possible (even if unlikely) usage. >>> When the idea of tags was presented as IETF, I had assumed that tags >>> would be versioned/managed entirely independently from the YANG modules >>> that the tags apply to. >> Well they are called "tags" after all. Normally one applies a tag to >> something (i.e., tags it. :) > Of course, I still mean that the tags are applied to the module, but > just that the place where that relationship is defined and maintained is > not in the module itself. I.e. some central locations that map from > unique module name to associated metadata tags. > > A roughly equivalent example might be perhaps like CDDB, where a program > can take a CD track, and go and fetch the associated metadata from some > known location without the metadata being embedded in the CD track itself.
Sure, but that is setup that way b/c the CD data is seen as read only right? I don't think this is even the normal way to tag things. There are tons of examples of the opposite where the item itself is tagged (XML attributes, social media's #hashtags, cow ears, ...). >>> For a while, there was a desire to organize YANG modules by their >>> hierarchical path location in the schema tree. My concern with this >>> approach, is that there needs to be sufficient foresight to get that >>> structure right now, because it will be very painful to change it in >>> future. Unfortunately things have a habit of evolving over time, and >>> hence choosing the right structure now such that is still the right >>> structure in 25 years seems somewhat unlikely. >>> >>> I was thinking that tags offers a better solution to this problem, that >>> allows the structure to be a bit more dynamic, evolving over time. I.e. >>> YANG modules for features can sit at (or near to) the top level of the >>> schema tree, and tags can then be used to group those modules into >>> sensible organizations that can evolve, so that when clients are trying >>> to sort through all the different YANG models that are available, they >>> have more hope than looking at a flat list. >> We in fact plan to do this with the device meta model. I believe this >> was in the presentation too, but it might not have been very obvious. >> >>> In this scenario, I think that it is better if the YANG module >>> definitions themselves don't specify the tags because then >>> adding/removing/changing them is going to be a pain. If this tag >>> information was managed separately (e.g. in something like YANG catalog) >>> then it seems easier for the tags to evolve over time. >> I want to be sure I understand you here. We've defined 3 places that a >> tag could be defined (comes into existence), the module designer, the >> vendor and the local user. When you say "module defines" are you talking >> about the first case, or are you talking about where a tag resides after >> it is created? > I was talking meaning the first case, where the tags are embedded in the > definition of a module, that itself is embedded in a published standard. > >> For the latter that was our intention with the yang >> library augmentation. For the former case consider e.g., IS-IS, I think >> the authors of that module know and are the appropriate folks to add >> categorization tags such as "ietf:routing", "ietf:protocol", >> "ietf:routing:igp" or whatever. > OK, today, it might seem obvious that the tags should be routing, > protocol, igp, etc. But in the future that choice of categorization > might not be the best, but it will be resistant to change because some > of the tag definitions are embedded in the modules themselves. > > Some of your suggested tags identify areas of IETF. But what if those > areas change over time, of the associated of drafts/WGs to particular > areas changes. A YANG module could end up being tagged with a stale > area, and I doubt that anyone would want to update a standard to just > update the tags. Lou didn't like the area tags either, so perhaps those are just poor initial choices, but "routing" (i.e., std tag "ietf:routing") is a fine tag I think, so maybe we need to move more to this rather than the ietf area groupings. > So, I was wondering if it wouldn't be better to not allow tags to be > embedded in the modules at all. Instead, if this was maintained in a > central database, e.g. like http://www.yangcatalog.org/, then the module > authors could always email the maintainers of YANG catalog to agree with > them how the module could most usefully be tagged in the catalog. If > this needs to change over time then this would seem to be much easier to > update. And then what happens to the modules that are deployed? I like having some set of tags than are paired directly with the standardized module specifically b/c they do not change. We did leave things open, so you could also create a yang catalog tag prefix and service as well. Thanks, Chris. >> Nothing would keep the user or vendor >> from removing these or adding their own tags for the same purpose as >> well if they found these inappropriate or incorrect. > OK, yes. But I wasn't thinking so much of a particular vendor or > operator, but more if the industry in general (or perhaps just the > maintainers of the catalog) decided that different categorization would > be more appropriate over time. > > Thanks, > Rob > >> >>> But I also had not really realized that the tags information would >>> necessarily reach down to the devices. I.e. I hadn't envisaged Chris's >>> example of querying the hello-time via an IGP package tag. Instead, I >>> had thought of tags making a YANG catalog website more useful. E.g. >>> when browsing for YANG modules, be able to restrict the query to just >>> the modules that are tagged as "standard" + "IGP", etc. >>> >>> So, I think that this draft may benefit with a bit more description of >>> the envisaged use cases, and also about how tags are envisaged to evolve >>> once they have been defined. >> Well one goal I had with tags was to allow for them to be used in >> the future in ways we may not have anticipated. Therefore >> we specifically did not lock down how they are used or what they are >> used for. That said, examples of how one might use could be helpful. >> >> Thanks, >> Chris. >> >>> Thanks, >>> Rob >>> >>>> Lou >>>> >>>> >>>>> Thanks, >>>>> Chris. >>>> >>>> _______________________________________________ >>>> netmod mailing list >>>> [email protected] >>>> https://www.ietf.org/mailman/listinfo/netmod >>>> . >>>>
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